Antioxidant properties of evening primrose seed extracts

The antioxidant activity of extracts of evening primrose seeds (SE) and a c ommercially extracted filter cake TC) were determined. The SE and FC were e xtracted with methanol/water (9:1) followed by evaporation and concentratio n. Extracts were tested in a bulk oil system and an oil-in-water emulsion u sing safflower oil as the major source of lipids. The antioxidant activity of the extracts was compared to that of a control and to that of butylated hydroxytoluene (BHT), singly, and in combination. Antioxidant activity was measured by the co-oxidation of beta -carotene, an oxidative stability inst rument, conjugated dienes, and headspace analysis of hexanal. The SE extrac t had greater antioxidant activity than the FC extract. The SE extract was more effective in controlling the oxidation in the oil-in-water model syste m than in the bulk oil system. The activity of SE was concentration depende nt, and at higher concentrations the SE was as effective as BI-IT, but it r equired higher concentrations because of its lack of purity. Synergism betw een SE and BHT was demonstrated in both model systems.